Surfactants have many end-use applications well known to those in the art wherein it is desirable to be able to alter and/or control the dissolution rate of the surfactant once it is intimately admixed with water. In certain situations, it becomes desirable to slow the rate at which the surfactants solubilize, for example, when used in toilet bowl cleaning cakes. More often, it is desired to increase the rate at which the solid surfactant dissolves into the aqueous medium. This enhanced rate of dissolution would be desirable, for example, in dishwashing or laundry powdered detergent situations. Heretofore, attempts to control the times of solid surfactant solubilization have taken various forms, such as using incorporated binders, extrusion granulation, membrane encapsulation, or tableting, i.e., compression of the surfactant-containing compositions all of which possess attendant disadvantages. For example, encapsulation is highly dependent upon the quality of the encapsulating material and may release the compositions in discrete packages. The compaction process is an extremely difficult way to control the release of surfactant material for slight variations in composition properties, e.g., tackiness, particle size, etc. can have dramatic impact on the dissolution rate even under fixed, uniform compacting pressure.
Extrusion processing to prepare melt-admixed granules, such as is taught in EP 501,798A1 has the disadvantage of always intimately admixing all of the components thus inherently placing a restriction on the individual components that can be utilized in such a process, i.e., they must be compatible. Furthermore, initially all of the material components will be exposed to the aqueous medium simultaneously, i.e., one cannot program for differing dissolution rates.
Granule-type products, i.e., multi-component particles are desirable in many end-use applications for they are more stable during storage and transport than mere physical mixtures of the dry individual components.
It would be advantageous if a process means relatively insensitive to minor process or product variations were available to avoid the above-identified problems of the prior art and to not only increase the rate at which nonionic solid surfactants dissolve in aqueous medium, but also permit i) incompatible components to be incorporated into a single particle and ii) preferential or sequential exposure of selected components to the aqueous media.